Sometimes they do.

depends on the letter, the agent and the buyer.

I think they are of no value.... the bottom line is the bottom line and buyers should either pay it or go on to the next home.... we encourage our sellers to keep the emotion out of the negotiating.... 

and as far as builders are concerned, it's show me the money.... they don't care about anyone's story.... and I make that clear to all buyer agents....

Only dealt with this once.  It made my sellers decision which to go with.

I have heard, here on AR, that they work.  In my market I would never recommend them and totally discourage them if asked.

Help IMO, I have had clients do it and the seller did relate to them. Some people selling a home don't care and just want the money, others have an emotional attachment and like thinking that someone will take care of their "special" house.

its a gamble...unless.... they are all about what they like about the home

It helps especially in a multiple offer situation.

It depends but typically most of my sellers want to see the bottom line.  

It depends on the particular seller.  In some cases, it may help, in other cases, it can hinder, and in yet other cases, it has no effect.

I think sellers ask a lot of questions like is the buyer qualified, married, with children , where do they work ,etc . So why not put it in writing 

Probably some of both, but I don't think they make too much of a difference in the majority of cases. I don't think they are used much anymore.

If the writer makes note of the clues the seller left behind, the letter will prove highly influential for offers of apparently equal value.

However, the seller response is not the greatest risk. The greater risk is when the buyer writes an inappropriate or ineffectual letter, or greatly flawed and you must intervene. One's writing is among the most personal and sensitive areas for which correction is not well received.  Take great care before allowing the buyer to 'free lance' in their composition or whether you provide the outline. Take care whose baby you call ugly. Make that mistake and the buyer will vaporize.

It may depend . Most sellers just want the best terms and highest price. 

Good morning Martin. I'm not sure how it could hurt. Folks want to sell to those they like and appreciating their home would be one way to accomplish that goal.

Make it a great weekend!

It helps the buyer but could hurt the seller if they get swayed by emotions. Realtors need to bring them back to reality & their best interest